Regulator valve

ABSTRACT

A control valve ( 1 ) comprises a housing ( 2 ) manufactured by a pressure die casting process, whose housing edges of upper semicircular bore hole are located exactly vertically above housing edges of lower semicircular bore hole and for this reason, the mold slide that forms the control edges ( 21 ) no longer has any contact point with the housing ( 2 ) and, as a consequence, symmetrical control edges ( 21 ) arise.

FIELD OF THE INVENTION

The invention concerns a control valve.

BACKGROUND OF THE INVENTION

Control valves whose housing is manufactured by a pressure die castingprocess have great friction hysteresis due to the mold inclines in thehousing and the asymmetrical control edges arising in this way. As aconsequence, an operating piston dips unilaterally into a bore hole inthe housing owing to which a unilaterally transverse acting force arisesduring the action of pressure upon the operating piston. In this way,frictional force arises in the longitudinal direction that always worksagainst an operating piston positioning force. This means that adifferential pressure arises from the control valve when approaching apressure point of a higher or lower pressure level. A difference inrelation to the same specified value arises between rising and fallingpressure. One thus speaks of a friction hysteresis. Owing to the moldinclines in the pressure die casting mold, great piston strokesadditionally arise between the two positions control edge or ventilationedge that are completely open. With spring activated operating pistons,a great spring force difference arises due to the large operating pistonstroke that leads to a rising or falling pressure course at differentpressures.

The objective of representing a control valve that has a small frictionhysteresis and, in this way, is especially suited for high standards ofexactitude; and, moreover, at the same time offers an economicalsolution that is not susceptible to disturbance, forms the basis of thepresent invention.

The objective underlying the invention is accomplished by arepresentative control valve that also has the characterizing featuresof the main claim.

SUMMARY OF THE INVENTION

In a housing manufactured with a pressure die casting process, the boreholes are precast. After the casting process, the boreholes are alwaysfirst shaped and subsequently the molded elements are pulled apart. Moldsliders that form the control edges no longer have contact points withthe housing, in the region of the bore holes, on account of which moldinclines can be dispensed within this region. With a control valvemanufactured according to the invention with a housing with bore holes,housing edges of the upper semicircular bore hole is located exactlyvertically over housing edges of the lower semicircular bore hole. Thismakes an easy shaping of the cast elements possible. When shaping thecast elements, a bore hole edge of the lower semicircular bore hole ofthe pressure die casting mold touches a bore hole edge of an uppersemicircular bore hole of the housing. Since at the time of contact, thecast element and pressure die casting mold have already been detachedfrom one another, no problems arise here. The normal mold incline thenruns above the bore hole edge of the upper semicircular bore hole sothat, in this region, the same shaping conditions are preserved. Withthe control valve manufactured according to the invention, due to thesymmetrical construction of the control edge no friction hysteresisarises. Due to the symmetrical construction of the control edges and theelimination of mold inclines, the stroke of the operating piston betweenthe two positions control edge or ventilation edge fully opened ishalved. Since the stroke of the operating piston is significantlyreduced, the risk of a spring force difference is minimized, owing towhich the pressures are approximately equal with a rising or fallingpressure curve. If need be, control edges with larger mold inclines canalso be constructed without the function of the control valve sufferingfrom this. The conversion of the construction known from thestate-of-the-art to that of the invention merely requires a conversionof tools.

Advantageous and appropriate refinements of the invention are indicatedin the dependent claims. The invention is, however, not restricted tothe combination of features of the claims. Rather, further suitablepossible combinations arise for the specialist from claims andindividual claim features on the basis of the specification.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in greater detail below on the basis ofa design represented in the drawings, wherein:

FIG. 1 illustrates the schematic structure of a control valve known onthe basis of the state-of-the-art and of a control valve of theinvention;

FIG. 2 illustrates a partial cut out of a pressure die casting mold ofthe control valve of the invention from FIG. 1; and

FIG. 3 illustrates a partial cut out of a housing of the control valveof the invention of FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The control valve of the invention, represented in FIG. 1, consists of ahousing 2, an operating piston 3 and a spring 4. At a constant controlpressure in a pressure channel 5, equilibrium forces exist on theoperating piston 3. If the control pressure in the pressure channel 5 israised, the operating piston 3 is additionally subjected to pressure, onits right side, that increases the axial force acting on the operatingpiston 3, due to which the operating piston 3 is displaced to the left.Due to the displacement of the operating piston 3, the spring 4 isrelieved. The spring force diminishes. A consequence thereof, a slit 7opens on a control edge 6 so that pressure medium can flow from apressure chamber 8 to a pressure chamber 9. Due to an obliquely runninghousing edge 10, the operating cylinder 3 must cover significant axialtravel before a slit opening results all around. The pressure in thepressure chamber 9 increases and acts through a bore hole 11 in theoperating piston 3 on a pressure chamber 12 and a face 13 of theoperating piston 3. When the equilibrium of forces is exceeded, thepressure building up in the pressure chamber 12 brings about adisplacement of the operating piston 3 to the right. Moreover, the slit7 continuously diminishes until it is completely closed. A highercontrol pressure then arises in the pressure chamber 8 corresponding tothe increased control pressure in the pressure channel 5. If, incontrast, the control pressure in the pressure channel drops, then theprocess runs in the reverse direction. A control edge 14 isasymmetrically constructed and consequently leads to a unilateraldipping of the operating piston 3 in a bore hole 15 owing to which aunilaterally transverse acting force on the operating piston 3 resultsduring the pressure action. The friction hysteresis arising, in thisway, is regarded as very disturbing during operation. A control edge 16,symmetrically constructed in the housing 2, results in an edge 17 of anupper semicircular bore hole being located exactly vertically above anedge 18 of a lower semicircular bore hole. In this way, the operatingpiston 3 evenly dips in the bore hole 15 and no transverse force arisesupon which the operating force 3 can act.

FIG. 2 depicts a partial cutout of a pressure die casting mold 19 of thecontrol valve 1 of the invention with associated shaping surface 20 andsymmetrical control edges 21.

A partial cutout of the housing 2 of the control valve 1 of theinvention is illustrated in FIG. 3. The section runs through the centerof the bore hole 15. The control edges 21 are constructed symmetricallycorresponding to the associated pressure die casting mold 19 representedin FIG. 1.

REFERENCE NUMBERS

-   1 Control valve-   2 Housing-   3 Operating piston-   4 Spring-   5 Pressure channel-   6 Control edge-   7 Slit-   8 Pressure chamber-   9 Pressure chamber-   10 Housing edge-   11 Bore hole-   12 Pressure chamber-   13 Face-   14 Face-   15 Bore hole-   16 Control edge-   17 Edge-   19 Pressure die casting mold-   20 Shaping surface-   21 Control edge

1. A control valve comprising: a pressure die cast housing including: acylindrical bore hole for receiving a cylindrical sliding piston, atapered chamber having an axis generally orthogonal to the bore hole andintersecting the bore hole with an inner surface formed of a housingedge wherein a plane defined by the inner surface of the chamberintersects the bore hole at an incline angle such that each point arounda circumference of an intersection between the plane of the innersurface of the chamber and the bore hole is non-symmetric with acorresponding diametrically opposing point around the circumference ofintersection and the chamber is formed during casting by a mold slidehaving a mold incline angle for removal of the mold slide from the casthousing, and a symmetric control edge formed between the chamber and thebore hole, and each point around a circumference of the control edge islocated opposite to a corresponding diametrically opposing point alongthe circumference.
 2. The control valve of claim 1, wherein: the piston(3) is biased in a first direction along the bore hole by a springlocated within the bore hole.
 3. The control valve of claim 2, furtherincluding: a pressure channel communicating with the bore hole in aregion of the spring to assist the spring in biasing the piston in thefirst direction.
 4. The control valve of claim 1, wherein: a mold slidethat forms the control edge does not have a common contact edge with thehousing edge.
 5. The control valve of claim 1, wherein: the housing edgein a region of the control edge does not include a mold incline angle.6. A pressure die cast housing for a control valve, the housingincluding: a cylindrical bore hole for receiving a cylindrical slidingpiston, a chamber having a longitudinal axis extending generallyorthogonal to a longitudinal axis of the bore hole and a conical innersurface formed of a housing edge and intersecting the bore hole at anincline angle wherein the chamber is formed during casting by a moldslide having a mold incline angle which facilitates removal of the moldslide from the cast housing a plane of the inner surface of the chamberintersects the bore hole such that each pant around a circumference ofan intersection between the plane of the inner surface of the chamberand the bore hole is non-symmetric with a corresponding diametricallyopposing point around the circumference of intersection, and a symmetriccontrol edge is formed between the chamber and the bore hole, and eachpoint around a circumference of the control edge is located opposite toa corresponding diametrically opposing point along the circumference. 7.A control valve manufactured by a pressure die casting process withhousing edges and control edges, and a control piston being locatedwithin a bore hole of the control valve and biased in one direction by aspring: wherein the housing edges and the control edges are formed suchthat the housing edges are conical and extend into the housing to form anon-symmetric intersection with the bore hole and the control edges areformed so that an edge of an upper semicircular region of a passage holeis exactly vertical aligned to an edge of a lower semicircular region ofthe bore so that opposed symmetric control edges are formed for thecontrol valve.